Communication networks have become necessary adjuncts to conducting business on a national and global scale. The existing voice and data networks provide fast and convenient facilities for people and machines to communicate with each other over long distances without the inconvenience of traveling in order to conduct business. These networks are also more reliable and more economical than other forms of communication.
While these networks adequately provide facilities for point-to-point communication, it is desirable to enhance these networks by allowing three or more customers to participate in a conference call wherein many customers can exchange information by voice and other means. An example of this might be an audio/video conference involving several remotely located business associates, each having a video terminal. In addition to video terminals, some of the conferees might have graphics units, electronic chalkboards, data terminals, etc., all of which can be used for communicating information in different forms. For convenience, these and other modes of communication will be referred to herein by the generic term "data" communication, and it is not intended that they be limited only to those modes that are mentioned above.
While voice conferencing arrangements have generally been known in the prior art, data conferencing is relatively new and has inherent differences that must be treated in a special manner. For example, in audio conferencing, the voice samples of all conferees that are concurrently speaking are added together, and the sum is distributed to each conferee. Each conferee hears a composite signal of the voices of all other conferees.
While each conferee on a data conference also must receive messages from other conferees, the data messages cannot simply be added together since the resultant sum would be meaningless and not representative of any data message. Thus, a data conference arrangement must process large volumes of individual messages to and from each conferee.
Also, the various data conferees may each have a different kind of terminal so that transmission speeds between the conferees may be different. Furthermore, one conferee may be using a graphics terminal while another conferee may be using an electronic chalkboard, and these terminals may not be compatible for direct communication with each other in terms of signaling and the protocol of messages between the units.
The prior art data conferencing arrangements avoid the above problems by restricting conferencing only to terminals that are compatible and/or establishing the conference with the aid of an attendant who manually switches the conferees together so that at any given time, one data terminal would broadcast to all other terminals of the same type.